US9284884B2ActiveUtilityA1
Trapped burned gas fraction control for opposed-piston engines with uniflow scavenging
Est. expiryJun 25, 2033(~7 yrs left)· nominal 20-yr term from priority
F01B 7/14F02B 39/04F02D 41/1458Y02T10/144F02D 2200/0411F02B 29/0418F02B 45/08F02D 41/0007F02M 25/0707F02D 43/00F02D 41/0072F02M 25/0727F02B 29/0412F02B 37/24F02B 75/282F02B 75/28F02D 41/0062F02M 35/1038F02B 33/00F01B 17/02F02D 2200/0402F02D 2041/141Y02T10/47F02D 21/08F02M 35/10386Y02T10/12F02M 26/23F02B 25/08F02M 26/05Y02T10/40Y02T10/30
79
PatentIndex Score
9
Cited by
44
References
15
Claims
Abstract
A trapped burned gas fraction is controlled in a two-stroke cycle opposed-piston engine with uniflow scavenging by adjusting an external EGR setpoint in real time. The adjusted setpoint is used to control EGR flow in the engine's air handling system.
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A uniflow-scavenged opposed-piston engine equipped with an air handling system, comprising:
at least one cylinder with a bore, longitudinally-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine;
a charge air channel to provide charge air to at least one intake port;
an exhaust channel to receive exhaust gas from at least one exhaust port;
an exhaust gas recirculation (EGR) loop having a loop input coupled to the exhaust channel and a loop output coupled to the charge air channel; and,
a control mechanization operable to:
determine a value of a trapped air handling parameter based on elements of combustion trapped in the cylinder by the last port of the cylinder to close during a cycle of engine operation and adjust the value of the trapped air handling parameter in response to a rate of EGR flow in the EGR loop; and
adjust the rate of EGR flow in the EGR loop based on the adjusted value of the trapped air handling parameter.
2. The opposed-piston engine of claim 1 , in which the control mechanization is operable to adjust the rate of EGR flow by operating a valve in the EGR loop to increase or decrease exhaust gas flow through the EGR loop.
3. The opposed-piston engine of claim 2 , in which the trapped air handling parameter is trapped burned gas fraction and the control mechanization is operable to:
determine a desired trapped burned gas fraction value for a current engine operating state;
determine a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determine an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio; and,
adjust EGR flow by operating the valve in the EGR loop in response to the error value.
4. The opposed-piston engine of claim 2 , in which the control mechanization is operable to correct the value of the trapped air handling parameter based upon a trapped temperature parameter.
5. The opposed-piston engine of claim 4 , in which the trapped air handling parameter is trapped burned gas fraction and the control mechanization is operable to:
determine a desired trapped burned gas fraction value for a current engine operating state;
determine a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determine an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio; and,
adjust EGR flow by operating the valve in the EGR loop in response to the error value.
6. A method of operating an opposed-piston engine, comprising:
generating exhaust gas in at least one ported cylinder of the engine;
transporting exhaust gas from an exhaust port of the ported cylinder through an exhaust channel;
recirculating a portion of the exhaust gas from the exhaust channel;
pressurizing fresh air;
mixing recirculated exhaust gas with the pressurized fresh air to form charge air;
pressurizing the charge air;
providing the charge air to an intake port of the ported cylinder;
determining a value of a trapped air handling parameter based on elements of combustion trapped in the cylinder by the last port of the cylinder to close during a cycle of engine operation;
adjusting the value of the trapped air handling parameter in response to a rate of EGR flow in the EGR loop; and
adjusting the rate of EGR flow in the EGR loop based on the adjusted value of the trapped air handling parameter.
7. The method of claim 6 , in which adjusting the rate of EGR flow includes operating a valve in the EGR loop to increase or decrease exhaust gas flow through the EGR loop.
8. The method of claim 7 , in which the trapped air handling parameter is trapped burned gas fraction and determining a value includes:
determining a desired trapped burned gas fraction value for a current engine operating state;
determining a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determining an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio; and,
adjusting EGR flow by operating the valve in the EGR loop in response to the error value.
9. The method of claim 7 , in which the control mechanization is operable to correct the value of the trapped air handling parameter based upon a trapped temperature parameter.
10. The method of claim 9 , in which the trapped air handling parameter is trapped burned gas fraction and determining a value includes:
determining a desired trapped burned gas fraction value for a current engine operating state;
determining a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determining an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio; and,
adjusting EGR flow by operating the valve in the EGR loop in response to the error value.
11. A uniflow-scavenged opposed-piston engine, comprising:
at least one cylinder with a bore, longitudinally-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine;
a charge air channel to provide charge air to at least one intake port;
an exhaust channel to receive exhaust gas from at least one exhaust port;
an exhaust gas recirculation (EGR) loop having a loop input coupled to the exhaust channel and a loop output coupled to the charge air channel; and,
a control mechanization operable to:
determine a trapped burned gas fraction value for a current engine operating state based on elements of combustion trapped in the cylinder by the last port of the cylinder to close during a cycle of engine operation;
determine a desired setpoint for EGR flow in the EGR loop for the trapped burned gas fraction value;
compare the desired setpoint with an actual rate of EGR flow in the EGR loop; and,
adjust the position of an EGR valve in the EGR loop based on the comparison.
12. The opposed-piston engine of claim 11 , in which the control mechanization is operable to adjust the actual rate of EGR flow in the EGR loop by adjusting the position of the EGR valve.
13. The opposed-piston engine of claim 12 , in which the control mechanization is operable to correct the trapped burned gas fraction based upon a trapped temperature value.
14. The opposed-piston engine of claim 13 , in which the control mechanization is operable to:
determine a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determine an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio;
correct the desired % EGR ratio based on the error; and,
adjust EGR flow by adjusting the position of the EGR valve based on the corrected desired % EGR.
15. The opposed-piston engine of claim 12 , in which the control mechanization is operable to:
determine a % EGR ratio defined by
%
E
G
R
=
W
egr
W
air
+
W
egr
in which W egr is a mass flow rate of EGR gas in the EGR loop and W air is a mass flow rate of air into the charge air channel;
determine an error value based upon a difference between a desired % EGR ratio and a measured % EGR ratio;
correct the desired % EGR ratio based on the error; and,
adjust EGR flow by adjusting the position of the EGR valve based on the corrected desired % EGR.Cited by (0)
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